EURURO Vol. 72 No. 4

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puncture . The Uro-Dyna-CT is a modified angiogra-
phy unit that allows the fluoroscopic unit to be rotated
around the patient, creating a similar image to the images
created by CT. Segmentation of the data acquired allows 3D
multiplanar reconstruction of the renal collecting system,
showing the exact path chosen for puncture. The C-arm is
placed in the ‘‘bull’s eye’’ position to indicate the puncture
site and its direction via a laser light. Once the needle is
inserted, the position can be confirmed via conventional
fluoroscopy and can be corrected if deemed necessary.
Puncture was successful in 9/12 patients tested, and in 7/9
cases the procedure was successful at the first attempt. The
average puncture time was 60 s, with an average planning
time of 6.5 min and an average radiation exposure dose of
5850 mGy/m2. This technique provides a 3D anatomical
image, and is fast, safe, and highly accurate when there is no
patient movement; moreover, the patient can be in the
supine position. Disadvantages are higher ionizing radiation
doses, a steep learning curve, and high costs. In addition,
excessive renal motility hampers the performance.
Ultrasonography using SonixGPS (UltraSonix, Richmond,
BC, Canada) navigation is another technological achieve-
ment in ultrasound-guided puncture . In this case, a
catheter is inserted via cystoscopy in the pyelocaliceal
system, with the patient in the lithotomy position. Then,
with the patient in the prone position, saline is instilled to
distend the pyelocaliceal system. A global positioning
system (GPS) electromagnetic transducer is in proximity
to the patient. An ultrasound scan is obtained using the
SonixGPS ultrasound probe in the area around the 11th and
12th rib edges, and the images acquired allow identification
of a suitable position and direction for the needle during
puncture. The direction, depth, and needle insertion angle
can be adjusted as needed, according to information
available in real time via the needle sensor. Using images
obtained via this technique, the needle, which includes an
electromagnetic sensor, is guided to the predetermined
calyx. This technique was tested in 25 patients with a
kidney stone, with 100% success for puncture at the first
attempt and an average puncture time of 5.5 min. It should
be noted that none of the patients in this study had a BMI
> 35 kg/m2, as fluoroscopy is still needed in obese patients.
Another disadvantage is that the patient anatomy is
obtained in 2D. A similar approach was reported by Chau
et al , who performed 18 PCNL cases using magnetic
field–based ultrasound navigation to visualize the position
of the needle tract in relation to the target calyx. Puncture
was performed freehand without a needle-guiding system
attached to the transducer. Needle deviation could be
detected and adjusted immediately to achieve a precise
puncture. Puncture was successful at the first attempt in
83.3% of cases.
Comparison of the above techniques to the one described
here highlights a few considerations. Puncture techniques
Table 1 – Advantages and disadvantages of new techniques for puncture of the renal colleting system
Study Technique Advantages Disadvantages
Bader et al Optical system in the
needle
Secure identification of the needle
Real-time needle visualization via
ultrasound
Easy handling and learning
No ionizing radiation
Needle redirection not possible in the
case of error trajectory
2D imaging
Difficult visualization in obese patients
Rassweiler et al iPad-assisted puncture Correct selection of the needle
location, angle, and trajectory
3D imaging
Correct visualization of anatomy
Minimal spatial errors
Short learning curve
Use of ionizing radiation
No real-time 3D image
Only minimal adjustments of the path allowed
Patient in prone position
Ritter et al Uro Dyna-CT 3D laser
guidance
3D anatomy imaging
Quick, safe, and highly accurate
Applicable in complex cases
Trajectory visualization in real
time and possibility of trajectory change
Higher ionizing radiation dose than
conventional technique
Technique hampered by excessive
renal motility
Steep learning curve
High cost
Li et al Ultrasonography using
Sonix GPS navigation
No ionizing radiation
Needle trajectory prediction
Operator can keep track of the needle
during the procedure
Allows adjustment of the trajectory
during the procedure
Easy to perform than conventional
puncture
In obese patients the ultrasound image
is highly impaired, and use of
fluoroscopy is recommended
2D image only
Chau et al Ultrasonography using
navigation system
under magnetic field
Present study Navigation using
electromagnetic sensors
No ionizing radiation
3D image of the needle trajectory in
real time
Position and orientation of the needle
in real time
Easy technical learning
Shorter execution time
Ability to redefine the trajectory
Procedure done in supine position.
Lack of visualization of anatomical
structures in the puncture path
Difficult to insert a ueteral catheter
with an electromagnetic sensor in
the desired calyx in situations in
which the calyx is fully occupied
by stones
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